I'm not fond of the karma system in the Ninja Gaiden games (UT spamming isn't fun to me). Based on the demo, the way to get high scores in Ninja Gaiden DS is all about killing your opponent quickly. There doesn't seem to be any bonuses for UT, however UT kill enemies the fastest. What I do is charge up an UT and then release it in the direction where the enemy will appear. So when the enemy spawns, they'll instantly die. So once you know where enemies come from, it'll be easy to know where to charge and what direction to release it in.

I'm not fond of the whole game it looks so bad even the backround is a image so its looks like few sprites are running in a cave backround etc. i know its good for ds but as a game its really bad in my opinion.